I've tried to use the umbrella and it doesn't work. What does it mean to "focus" on an enemy? Nothing seems to work. If any one can help I would appreciate it.

The Menacing Ruin is a rather easy mini-type-boss that can be defeated with a little strategy. Just use the umbrella when he throws the fire ball and it reflects on him and then his hands fall down and the rest is easy. Hope I helped. He will appear a lot in the future. (by the way.)

okay, defeating the Menacing Ruin is simple as long as you know how to avoid and dodge it's attack while battling.
When you facing it, don't ever us the pepper grinder, the menacing ruin will catch the burning pepper and throw back at alice.
Use the teapot cannon to destroy the first two heads easily (you can destroy the third one as well but it will take a few more hits). Remember to use the umbrella to reflect the fire balls it throws at you to destroy the doll arms. Once you destoryed the arms, you can either use the hobby horse or the vorpal blade to finish off the remaining head(s), but remember to dodge the any attacks using the butterfly warp. Hope this helps :)

Use the umbrella to reflect attacks, use the Vorpal Blade when it's lost focus

After you shatter one of its arms off by deflecting its attacks with the umbrella either spam the teapot cannon.

Or use the teapot cannon to shatter the first two heads then finish off the last head with the Vorpal Blade.

I got it guys. Thanks so much. Now, I have to perfect defeating Colossal Ruin and I'll be set.

Yes I do. When that ruin throws a fireball, you use an umbrella. Also, if it charges, use dodge. Use a pepper grinder or a teapot cannon in case The Menacing Ruin doesn't throw a fireball or charges, aim at the doll faces.. One more tip, it is very important, when your health is very low, unleash.... HYSTERIA!!!!!!!! Comment me if this works. That is my advice for you.